British Columbia Recovery Strategy Series
Recovery Strategy for the Sharp-tailed Snake
(Contia tenuis) in British Columbia
Prepared by the Sharp-tailed Snake Recovery Team
August 2008
DRAFT
About the British Columbia Recovery Strategy Series
This series presents the recovery strategies that are prepared as advice to the Province of British
Columbia on the general strategic approach required to recover species at risk. The Province
prepares recovery strategies to meet its commitments to recover species at risk under the Accord
for the Protection of Species at Risk in Canada, and the Canada – British Columbia Agreement
on Species at Risk.
What is recovery?
Species at risk recovery is the process by which the decline of an endangered, threatened, or
extirpated species is arrested or reversed, and threats are removed or reduced to improve the
likelihood of a species’ persistence in the wild.
What is a recovery strategy?
A recovery strategy represents the best available scientific knowledge on what is required to
achieve recovery of a species or ecosystem. A recovery strategy outlines what is and what is not
known about a species or ecosystem; it also identifies threats to the species or ecosystem, and
what should be done to mitigate those threats. Recovery strategies set recovery goals and
objectives, and recommend approaches to recover the species or ecosystem.
Recovery strategies are usually prepared by a recovery team with members from agencies
responsible for the management of the species or ecosystem, experts from other agencies,
universities, conservation groups, aboriginal groups, and stakeholder groups as appropriate.
What’s next?
In most cases, one or more action plan(s) will be developed to define and guide implementation
of the recovery strategy. Action plans include more detailed information about what needs to be
done to meet the objectives of the recovery strategy. However, the recovery strategy provides
valuable information on threats to the species and their recovery needs that may be used by
individuals, communities, land users, and conservationists interested in species at risk recovery.
For more information
To learn more about species at risk recovery in British Columbia, please visit the Ministry of
Environment Recovery Planning webpage at:
<http://www.env.gov.bc.ca/wld/recoveryplans/rcvry1.htm>
Recovery Strategy for the Sharp-tailed Snake
August 2008
Recovery Strategy for the Sharp-tailed Snake (Contia tenuis) in British
Columbia
Prepared by the Sharp-tailed Snake Recovery Team
August 2008
Recovery Strategy for the Sharp-tailed Snake
August 2008
Recommended citation
Sharp-tailed Snake Recovery Team. 2008. Recovery Strategy for the Sharp-tailed Snake (Contia
tenuis) in British Columbia. Prepared for the B.C. Ministry of Environment, Victoria, BC. 27 pp.
Cover illustration/photograph
Contia tenuis, juvenile, Saltspring Island, BC. Photo by Kristiina Ovaska
Additional copies
Additional copies can be downloaded from the B.C. Ministry of Environment Recovery Planning
webpage at:
<http://www.env.gov.bc.ca/wld/recoveryplans/rcvry1.htm>
Publication information
ISBN 978-0-7726-6055-8
Cataloguing in Publication: Pending
Content (excluding illustrations) may be used without permission, with appropriate credit to the
source.
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Recovery Strategy for the Sharp-tailed Snake
August 2008
Disclaimer
This recovery strategy has been prepared by the Sharp-tailed Snake Recovery Team, as advice to
the responsible jurisdictions and organizations that may be involved in recovering the species.
The British Columbia Ministry of Environment has received this advice as part of fulfilling its
commitments under the Accord for the Protection of Species at Risk in Canada, and the Canada
— British Columbia Agreement on Species at Risk.
This document identifies the recovery strategies that are deemed necessary, based on the best
available scientific and traditional information, to recover Sharp-tailed Snake populations in
British Columbia. Recovery actions to achieve the goals and objectives identified herein are
subject to the priorities and budgetary constraints of participatory agencies and organizations.
These goals, objectives, and recovery approaches may be modified in the future to accommodate
new objectives and findings.
The responsible jurisdictions and all members of the recovery team have had an opportunity to
review this document. However, this document does not necessarily represent the official
positions of the agencies or the personal views of all individuals on the recovery team.
Success in the recovery of this species depends on the commitment and cooperation of many
different constituencies that may be involved in implementing the directions set out in this
strategy. The Ministry of Environment encourages all British Columbians to participate in the
recovery of the Sharp-tailed Snake.
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Recovery Strategy for the Sharp-tailed Snake
August 2008
RECOVERY TEAM COMPOSITION
Members (August 2008)
Trudy Chatwin
Laura Friis
Purnima Govindarajulu
Pat Gregory
Leigh Anne Isaac
Laura Matthias
Kari Nelson
Kristiina Ovaska
Marilyn Fuchs
Brian Reader
Mike Waters
B.C. Ministry of Environment
B.C. Ministry of Environment
B.C. Ministry of Environment
University of Victoria
University of Victoria
Salt Spring Island Conservancy
B.C. Ministry of Environment
Biolinx Environmental Research Ltd. and
Department of Forest Sciences, University of
British Columbia (UBC)
Capital Regional District Parks
Parks Canada
Canadian Forces Base (CFB) Esquimalt,
Department of National Defence
Observers (August 2008)
Todd Carnahan
Dave Cunnington
Arthur Robinson
Andrea Schiller
Ardice Todosichuck
Habitat Acquisition Trust
Environment Canada
Canadian Forest Service
Canadian Forest Service
Islands Trust
Scientific Advisor
Christian Engelstoft
Alula Biological Consulting
AUTHORS
See Acknowledgements.
RESPONSIBLE JURISDICTIONS
The British Columbia Ministry of Environment is responsible for producing a recovery strategy
for the Sharp-tailed Snake under the Accord for the Protection of Species at Risk in Canada.
Other provincial and federal government agencies that contributed to the preparation of this
recovery strategy include Parks Canada, Canadian Forest Service, and CFB Esquimalt,
Department of National Defence.
ACKNOWLEDGEMENTS
Members of the Sharp-tailed Snake Recovery Team, past and present, have participated in the
preparation of this or previous versions of the recovery strategy. Thanks in particular to Kristiina
Ovaska for drafting and revising this strategy. Louise Blight and Christian Engelstoft contributed
to an earlier draft. Special thanks to Christian Engelstoft for sharing his unpublished data and
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Recovery Strategy for the Sharp-tailed Snake
August 2008
providing updates on distribution, habitats, and stewardship efforts. The Habitat Conservation
Trust Funds’ Species at Risk Restricted Account funded the preparation of the strategy. Thanks
to Jenny Feick and Robert Weaver for valuable review comments and to David Fraser, David
Cunnington, and Arthur Robinson for their contributions to the recovery team. The recovery
team extends a special thank you to all the landowners who have taken an interest in protecting
this species and its habitat.
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Recovery Strategy for the Sharp-tailed Snake
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EXECUTIVE SUMMARY
The Sharp-tailed Snake, Contia tenuis, is a small, non-venomous, secretive snake endemic to
western North America. Its range extends from British Columbia (B.C.) south to western
California. The species has an extremely limited Canadian distribution within a relatively
densely populated part of southwestern B.C. As of March 2008, distribution records exist from
10 sites located in the Gulf Islands (North and South Pender, Saltspring, Galiano) and southern
Vancouver Island. All recent records are from the Capital Regional District (Victoria, BC),
where pressures on remaining natural areas are intense due to a rapidly growing human
population.
Suitable habitats for the species are naturally fragmented, but threats to the persistence of
populations are largely human-induced. The main threats are from habitat loss, fragmentation,
and degradation, primarily due to urbanization and the development of associated infrastructures.
The loss or degradation of potential oviposition and hibernation habitats is of particular concern;
rocky slopes with a southern exposure in small forest openings are thought to be important
habitat features for these functions. Road mortality is a threat, but its significance to populations
is unknown.
The long-term goal for recovery is to ensure the persistence of the Sharp-tailed Snake across its
natural range in Canada. The short-term goal is to ensure the persistence of Sharp-tailed Snake
populations at each known site and to prevent the loss of important habitats. The objectives for
the next 5 years are to (1) protect all known Sharp-tailed Snake habitats and populations; (2)
prevent fragmentation of habitat within occupied sites; (3) investigate the existence of additional
populations throughout the species’ Canadian range, including suitable habitats outside the
known range within the Georgia Depression Ecoprovince; (4) protect habitats important to the
species’ survival and recovery as they are identified; (5) continue to reduce gaps in our
knowledge of habitat requirements; (6) continue to reduce gaps in our knowledge of the species’
population ecology; and (7) increase awareness of the Sharp-tailed Snake and its habitats. This
recovery strategy addresses the above objectives and responds to identified threats, while
building on existing and ongoing recovery work and on collaborative efforts that have already
been established with various agencies, organizations, and landowners.
The approaches to meet the recovery objectives have been grouped into the following broad
strategies: habitat protection, habitat stewardship, habitat inventory, population inventory,
research, and outreach. The primary focus is habitat protection to ensure that further loss and
fragmentation of habitats are prevented. The approach involves collaborating with land managers
and local planners to incorporate habitat protection needs of this species into the planning
process and examining opportunities for land acquisitions and covenants. Because several sites
are on private lands within residential areas, initiating and continuing stewardship activities with
landowners is also a priority.
Several new localities for the Sharp-tailed Snake have been discovered over the past few years
through increased search effort and public awareness programs; additional populations may well
exist. Habitat assessment throughout the species’ range, along with surveys for snakes, will help
delineate the species’ Canadian distribution more accurately and is the first step towards the
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Recovery Strategy for the Sharp-tailed Snake
August 2008
protection of habitats at new sites. Inventory efforts should also focus on known sites to provide
information on the extent of local distribution and on areas with historical records. Threats
dealing with habitat degradation and inadvertent mortality of snakes are largely addressed
through outreach, such as strategic distribution and display of stewardship and interpretive
materials, delivery of workshops, and other initiatives that increase public awareness of the
snakes and their habitats.
Research is needed to clarify threats from road mortality and to fill in data gaps on habitat use,
genetic structure of populations, demographic patterns, and life history. The most urgent need is
to collect information necessary to identify critical habitats, including seasonal pattern of habitat
use, movements, and important micro- and macro-habitat features. An action plan that identifies
activities needed to implement the recovery strategies is in preparation, to be completed before
or by 2015.
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Recovery Strategy for the Sharp-tailed Snake
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TABLE OF CONTENTS
RECOVERY TEAM COMPOSITION ............................................................................................................iii
AUTHORS.....................................................................................................................................................iii
RESPONSIBLE JURISDICTIONS ................................................................................................................iii
ACKNOWLEDGEMENTS .............................................................................................................................iii
EXECUTIVE SUMMARY .............................................................................................................................. v
LIST OF TABLES AND FIGURES ...............................................................................................................vii
BACKGROUND ............................................................................................................................................ 1
Species Assessment Information from COSEWIC................................................................................... 1
Description of the Species ........................................................................................................................ 1
Populations and Distribution ..................................................................................................................... 1
Needs of the Sharp-tailed Snake.............................................................................................................. 4
Habitat and biological needs ................................................................................................................ 4
Ecological role ...................................................................................................................................... 5
Limiting factors ..................................................................................................................................... 5
Threats...................................................................................................................................................... 5
Threat classification.............................................................................................................................. 6
Description of threats ........................................................................................................................... 8
Actions Already Completed or Underway............................................................................................... 11
Knowledge Gaps .................................................................................................................................... 13
RECOVERY ................................................................................................................................................ 14
Recovery Feasibility................................................................................................................................ 14
Recovery Goal ........................................................................................................................................ 15
Rationale for the Recovery Goal............................................................................................................. 15
Recovery Objectives............................................................................................................................... 15
Approaches Recommended to Meet Recovery Objectives.................................................................... 16
Recovery planning table..................................................................................................................... 17
Description of the recovery planning table ......................................................................................... 18
Performance Measures .......................................................................................................................... 19
Critical Habitat......................................................................................................................................... 20
Identification of the species’ critical habitat ........................................................................................ 20
Recommended schedule of studies to identify critical habitat ........................................................... 21
Existing and Recommended Approaches to Habitat Protection............................................................. 21
Effects on Other Species ........................................................................................................................ 23
Socioeconomic Considerations .............................................................................................................. 23
Statement on Action Plans ..................................................................................................................... 23
REFERENCES............................................................................................................................................ 24
PERSONAL COMMUNICATIONS.............................................................................................................. 26
LIST OF TABLES AND FIGURES
Figure 1. Distribution of the Sharp-tailed Snake in western North America (A) and in southwestern British
Columbia (B).. ............................................................................................................................................... 3
Table 1. Threat classification table for the Sharp-tailed Snake. ................................................................... 6
Table 2. Recovery planning table for the Sharp-tailed Snake. ................................................................... 17
Table 3. Schedule of studies required for the identification of critical habitat............................................. 21
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Recovery Strategy for the Sharp-tailed Snake
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BACKGROUND
Species Assessment Information from COSEWIC
Date of Assessment: April 1999
Common Name (population): Sharp-tailed Snake
Scientific Name: Contia tenuis
COSEWIC Status: Endangered
Reason for Designation: This species occurs in low numbers and has a highly fragmented
distribution. Area of occupancy is less than 10 km². The species has low fecundity and low
potential of increase with no chance of a rescue effect.
Canadian Occurrence: British Columbia
Status history Designated Endangered in April 1999. Status re-examined and confirmed in
October 1999. Last assessment based on an existing status report.
Description of the Species
The Sharp-tailed Snake, Contia tenuis, is a small, harmless snake endemic to western North
America. Adults are slender (about the thickness of a pencil) and about 20–30 cm in total length.
The back and sides are brown or reddish brown and the underside has characteristic black and
white barring; juveniles are typically more brightly coloured than adults. The short tail ends in a
small thorn-like scale, which gives the species its common name.
Populations and Distribution
The range of the Sharp-tailed Snake extends from southwestern British Columbia (B.C.) south
through Washington and Oregon to central California. Populations occur at scattered locations in
the northern portion of the species’ range in B.C. and Washington (Leonard and Ovaska 1998),
whereas the distribution is more continuous and populations appear to be larger in Oregon and
California (Cook 1960; Hoyer et al. 2006). Recent morphological and genetic evidence suggest
that two distinct forms of the Sharp-tailed Snake exist (Crother et al. 2001). A long-tailed form is
found in coastal areas of California and parts of southern Oregon and may represent a separate
species (Hoyer 2001; Feldman and Spicer 2002). Snakes from the remainder of the species’
distribution—in the interior of California, most of Oregon, Washington, and B.C.—constitute
another form. Specimens from B.C. are genetically similar to those from Washington and
Oregon at the species level, based on analysis of a small number of samples from the province
(M. Blouin, pers. comm., 2001; C. Feldman, pers. comm., 2008). Finer scale differences, such as
among populations on different Gulf Islands, remain to be investigated.
In Canada, the Sharp-tailed Snake has an extremely limited distribution and is known from only
a few localities in southwestern B.C. The extent of occurrence 1 is about 1200 km2, calculated
using the minimum polygon method from records since the 1940s. The area of occupancy1 is less
than 10 km2. Although these populations represent a small proportion of the world distribution
and abundance of the species (about 5% in terms of extent of occurrence based on a total range
1
As defined by COSEWIC (<http://www.cosewic.gc.ca/eng/sct0/Assessment_process_tbl3_e.cfm>).
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Recovery Strategy for the Sharp-tailed Snake
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of 25,000 km2; NatureServe 2007), they may be important reservoirs of genetic variability and
may contain unique ecological adaptations.
In B.C., the Sharp-tailed Snake has been recorded from North Pender, South Pender, Saltspring,
and Galiano islands in the southern Gulf Islands, and from the southern tip of Vancouver Island
(Spalding 1993, 1995; COSEWIC 1999; Engelstoft 2004, 2005, 2006, 2007). Where these
occurrences 2 are separated by dispersal barriers such as major water bodies, or by distances of
more than 5 km, they are considered to represent different sites (NatureServe 2007). Whether
sites on the same island represent separate populations is unknown. Since the preparation of the
COSEWIC status report, four new sites have been found: three on southern Vancouver Island
and one on Saltspring Island (Engelstoft 2004, 2005, 2006, 2007, and pers. comm., 2008). The
area of occupancy at the previously known sites on Saltspring, Vancouver, and South Pender
islands has increased slightly due to new records from different points within these sites (C.
Engelstoft, pers. comm., 2008). The species is known from only one site record on Galiano
Island, in 1981 (Spalding 1993, 1995). In total, since the 1940s, the species has been recorded
from 10 sites in southwestern B.C. (Figure 1). An additional, isolated record exists from near
Chase in the B.C. Interior (Tanner 1967), but its validity is questionable (Leonard and Ovaska
1998).
Population sizes and trends are poorly known. At four sites where the species has been studied
through capture-recapture studies over several years (one site each on Saltspring and North
Pender; two sites on Vancouver Island), the number of individual snakes detected ranged from
13 to more than 50. This variation reflected both sampling effort and the size of the areas
surveyed. Analysis of mark-recapture data at the most intensively studied site on North Pender
resulted in a mean population estimate of 49 snakes (95% confidence interval: 43–65 snakes) and
mean density of 0.067 snakes per square metre (Govindarajulu et al., in prep.). Over a 6-year
period, from 1997 to 2002, this population was stable or slightly declining (growth rate = 0.89;
95% confidence interval: 0.79–1.1).
Globally, the Sharp-tailed Snake is ranked as G5 (secure) (NatureServe 2007). Subnational
rankings are S5 (California), S4 (Oregon), S2 (Washington), and S1 (British Columbia).
2
An area in which a species is, or was, present.
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Recovery Strategy for the Sharp-tailed Snake
A
August 2008
B
Galiano
Island
Saltspring
Island
Pender
Islands
Vancouver
Island
Victoria
Figure 1. Distribution of the Sharp-tailed Snake in western North America (A) and in southwestern
British Columbia (B). “?” in Panel A indicates a questionable record from near Chase, BC. Panel B shows
southern tip of Vancouver Island and southern Gulf Islands. Dashed line indicates the boundary of the
Capital Regional District. Occurrences less than 5 km apart are shown as a polygon, representing a single
site. Sources: Panel A, COSEWIC (1999); Panel B, courtesy of Christian Engelstoft, March 2008.
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Recovery Strategy for the Sharp-tailed Snake
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Needs of the Sharp-tailed Snake
Habitat and biological needs
All confirmed distribution records for the species are from the Coastal Douglas-fir (CDF)
biogeoclimatic zone, which encompasses a narrow strip of land on the southeast coast of
Vancouver Island and adjacent Gulf Islands, and also includes a fringe of the mainland coast
(Meidinger and Pojar 1991). This zone covers about 200,000 ha, most of which is below 150 m
in elevation (MacKinnon and Eng 1995).
The Sharp-tailed Snake has been found in relatively open-canopy forest dominated by Douglasfir (Pseudotsuga menziesii) and arbutus (Arbutus menziesii) (COSEWIC 1999). Some of the sites
on Vancouver Island and Saltspring Island contain Garry oak (Quercus garryana) or are within a
matrix of Garry oak and associated ecosystems (Engelstoft 2004 and pers. comm., 2008). Garry
oak ecosystems are Red-listed (critically imperiled) in the province. Many Sharp-tailed Snake
sites on Vancouver Island are on rocky hillsides in open woodland habitats dominated by
Douglas-fir and arbutus. Several Douglas-fir–arbutus ecosystems in the CDF biogeoclimatic
zone are at risk (B.C. MOE 2008).
Suitable habitats for the Sharp-tailed Snake must provide thermoregulation, oviposition,
hibernation, and aestivation sites, as well as foraging opportunities in a spatial pattern that is
within the movement capabilities of individual snakes. COSEWIC (1999) identified the
availability of suitable oviposition sites as an important, potentially limiting factor for the Sharptailed Snake in B.C. and suggested that rocky, south-facing slopes in small forest openings
provide such habitat. Brodie et al. (1969) suggested that a paucity of suitable exposed southern
slopes, especially those with talus, was responsible for the concentration of reptiles, including the
Sharp-tailed Snake, at a communal egg-laying site in Oregon. No eggs of this species have ever
been found in B.C., but the presence of hatchling-sized young at a rocky slope supports the
suggestion that such habitats are important for reproduction (Engelstoft and Ovaska 1999). In
addition to oviposition sites, rocky slopes may provide suitable thermoregulation and hibernation
sites for the snakes (Engelstoft and Ovaska 1999). Habitat features at sites where the Sharp-tailed
Snake was found tended to have southern exposure, shallow soil and leaf litter, and a high cover
of rock when compared with random points 50 m away (Wilkinson and Gregory 2005).
The availability of refuges appears to be important for all activities, as the snakes are seldom
found in the open, away from cover-objects. The Sharp-tailed Snake has been found under and
within decaying logs (COSEWIC 1999), but the importance of coarse woody debris as a habitat
component for the species is unclear. Similarly, foraging habitats of the snakes are poorly
understood. The snakes feed on small invertebrates, primarily slugs; presumably, during their
active season, they require proximity to moist areas where slugs are abundant.
Limited information collected to date on movements indicates that individual snakes confine
their activities to relatively small areas during the active season from spring to autumn. Within a
rural residential area on North Pender Island, individuals used an area usually less than 55 m
along the greatest dimension at a site (Engelstoft and Ovaska 1999). In relatively undisturbed
habitat, individual snakes moved straight-line distances of up to 31 m (Ovaska and Engelstoft
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Recovery Strategy for the Sharp-tailed Snake
August 2008
2005). There was no evidence at either site of extensive seasonal migrations between habitats,
such as that undertaken by some other species of snakes. The Sharp-tailed Snake is thought to
spend much of its time underground (Cook 1960; COSEWIC 1999), but virtually nothing is
known of its underground habitat use or requirements. Whether the species is associated with
particular terrain features (such as fissures in bedrock) or geomorphologies is unknown.
The Sharp-tailed Snake can coexist with humans, provided that sufficient cover and other habitat
features are retained. In California and Oregon, many observations are from backyards and other
disturbed areas within or near urban areas (Cook 1960; Hoyer et al. 2006). In B.C., the snakes
have been found in compost heaps, borders of gardens, and woodpiles within low-density
residential areas, and they readily use artificial cover-objects constructed of wood, metal, or
asphalt roofing (Engelstoft and Ovaska 1999; C. Engelstoft, pers. comm., 2008).
Ecological role
The Sharp-tailed Snake is a unique component of the forest ecosystems that it occupies,
including rare Garry oak–arbutus habitats. The snakes are important in the food web both as
predators of slugs and other invertebrates and as prey for various vertebrates. They are thought to
be beneficial to humans as they feed mainly on slugs, including introduced garden pests (Zweifel
1954; Cook 1960).
Limiting factors
The small Canadian range and localized distribution pattern of the Sharp-tailed Snake are
probably due to past climatic conditions and historical factors rather than to human activities
(COSEWIC 1999). In B.C., climate probably limits northward range expansion of the Sharptailed Snake. Present-day populations may represent remnants of a wider past distribution during
periods when conditions were more suitable for egg-laying reptiles, such as during the warmer
Hypsithermal Interval about 8500–5000 years ago (COSEWIC 1999).
The Sharp-tailed Snake is one of two egg-laying (oviparous) squamates 3 that occur in coastal
B.C.; the other is the non-native European Wall Lizard, Podarcis muralis. In reptiles, incubation
temperatures influence both developmental rates and phenotypic traits of offspring, which in turn
can affect survival (Burger 1998). The availability of nest sites with appropriate thermal
conditions thus plays an important role in determining the distribution of oviparous species
(Shine 2004), and probably limits the distribution of the Sharp-tailed Snake to certain habitats in
the southern part of the province.
Threats
Current threats to the persistence populations of the Sharp-tailed Snake are largely humaninduced (COSEWIC 1999). The Coastal Douglas-fir biogeoclimatic zone where the species
occurs is one of the most modified ecosystems in the province (MacKinnon and Eng 1995), and
land conversions and development of remnant forest habitats continue at a rapid rate. These
3
Snakes and lizards.
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Recovery Strategy for the Sharp-tailed Snake
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threats may be compounded with natural sources of mortality due to predation or adverse
climatic conditions, especially in small habitat patches. Small isolated populations are inherently
vulnerable to disturbances and chance events.
The main human-caused threats to the species include (1) habitat loss; (2) habitat fragmentation
at broad and fine scales; (3) habitat degradation; and (4) road mortality. Additional threats that
may affect local populations include (5) predation by domestic and feral animals; (6) use of
molluscides and other pesticides; and (7) direct persecution of snakes (Table 1). Most of the
above threats are associated with increasing residential development and construction and
improvement of roads and other associated infrastructure.
Threat classification
Table 1. Threat classification table for the Sharp-tailed Snake.
1
Urban development
Threat attributes
Threat
category
General
threat
Specific
threat
Stress
2
Habitat loss
Residential development,
land clearing, road
construction, quarrying
Disturbance of habitats
needed for essential life
history functions
Reduced survival and
reproductive success;
accidental mortality
Extent
Local
Range-wide
Occurrence
Historical & ongoing
Historical & ongoing
Frequency
High
High
Causal certainty
High
High
Severity
High
High
Urban development
Threat attributes
Threat
category
Habitat fragmentation at
broad and fine scales
Extent
General
threat
Residential development,
land clearing, road
construction
Specific
threat
Barriers to movements
Stress
Isolation and
fragmentation of
populations
3
Local
Range-wide
Occurrence
Historical & ongoing
Historical & ongoing
Frequency
High
High
Causal certainty
Moderate
Unknown
Severity
Moderate
Unknown
Habitat degradation
General
Lawn mowing;
Moderate
Level of concern
Gardening and landscaping
activities
Threat
category
High
Level of concern
Threat attributes
Extent
Local
Occurrence
Range-wide
Ongoing
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Recovery Strategy for the Sharp-tailed Snake
threat
mechanical weed
trimming; removal of
rocks and other shelter;
burning; facilitating
spread of invasive plants
Specific
threat
Loss of shelter;
degradation of oviposition
sites; accidental mortality
Stress
Reduced survival or
productivity; accidental
mortality
4
Road mortality
General
threat
Accidental mortality
while crossing roads or
using roadside habitats
Specific
threat
Decreased survival
probability
Stress
Excessive loss of
juveniles or breeding
adults, resulting in a
population decline
5
Threat
category
Recurrent
Causal certainty
Moderate
Severity
Low moderate,
depending on
intensity of activities
Moderate
Level of concern
Threat attributes
Extent
Local
Occurrence
Frequency
Causal certainty
Severity
Predation by domestic or
feral animals
Cats, birds
Specific
threat
Mortality from predation
Stress
Excessive loss of
juveniles or breeding
adults, resulting in a
population decline
Range-wide
Historical and
ongoing
Recurrent
(documented at 2
sites)
High
Unknown
Moderate
Level of concern
Predation
General
threat
6
Frequency
Road construction and
improvements
Threat
category
August 2008
Threat attributes
Extent
Local
Range-wide
Occurrence
Continuous
Frequency
Unknown
(documented at 1
site)
Causal certainty
Severity
High
Unknown
Low-Moderate
Level of concern
Pesticides & herbicides
Threat attributes
Threat
category
Use of pesticides,
especially molluscides,
and herbicides
Extent
General
Contamination of
Occurrence
Local
Range-wide
Unknown
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Recovery Strategy for the Sharp-tailed Snake
threat
Specific
threat
foraging areas and loss of
prey; contamination of
snakes
Loss of foraging
opportunities; poisoning
Frequency
Causal certainty
Severity
Stress
7
Mortality or reduced
survival or productivity
Persecution
General
threat
Wanton killing of snakes
by humans
Specific
threat
Death
Stress
Reduced survival
probability; population
decline
Recurrent
Low – moderate,
depending on
chemicals used
Moderate
Low – moderate
Level of concern
Persecution
Threat
category
August 2008
Threat attributes
Extent
Local
Occurrence
Unknown
Frequency
Recurrent
Causal certainty
Severity
Level of concern
Range-wide
High
Unknown
Low
Description of threats
1. Habitat loss
Primary threats to the habitat of the Sharp-tailed Snake consist of expanding urbanization,
including housing developments and associated road building and infrastructure development.
These developments are concurrent with an expanding human population throughout the species’
range on the Gulf Islands and southern Vancouver Island. Further habitat loss is a major threat to
the Sharp-tailed Snake because of low numbers of populations and individuals and small
Canadian range of the species. The loss of any population would reduce probability of
persistence and opportunities to conserve the species.
The eastern coastal lowlands of Vancouver Island and the adjacent Gulf Islands are one of the
most extensively modified and fragmented areas of the province. Most of this area (92.1%)
consists of urban or rural landscapes or forests less than 100 years old (Ward et al. 1998).
Woodland ecosystems are widely scattered and comprise only 0.6% of the area (Ward et al.
1998). Remnant woodland ecosystems consist of open forests dominated by Garry oak, Douglasfir–Garry oak, or Douglas-fir–arbutus and often occur on south-facing rocky knolls and exposed
bedrock; the Sharp-tailed Snake often use such areas.
All recent Sharp-tailed Snake records are from within the Capital Region, which covers the
extreme southern portion of Vancouver Island and includes the Gulf Islands from Galiano Island
southwards. According to the Sensitive Ecosystems Inventory, only about 6200 ha of older forest
(i.e., > 100 years) remains within this area (CRD 2003). Most of the remaining older forest is in
the Western Communities (i.e., the western districts and municipalities of the Capital Regional
District; about 4500 ha) and the Gulf Islands (about 1200 ha). Garry oak ecosystems are
8
Recovery Strategy for the Sharp-tailed Snake
August 2008
extremely rare, with a small fraction remaining from their original coverage (about 512 ha
remaining in 1997 compared to estimated 10,443 ha in the 1800s) (GOERT 2007).
The pressure on the remaining natural areas within the Capital Region is intense due to increased
human population growth. From 1991 to 2001, the population within the Capital Region
increased by 8.2% (CRD 2008a). The fastest growing areas were the Western Communities
(16.6%) and Gulf Islands (18.2%); in both areas, most of the population expansion took place
during the first half of the 10-year period. Population growth and associated rate of land
conversions will most likely continue in these relatively undeveloped areas over the next decade.
Western Communities and Gulf Islands are forecast to experience growth rates of 92.1% and
43.5%, respectively, by 2026 relative to population sizes in 1996 (CRD 2008a).
2. Habitat fragmentation at broad and fine scales
Suitable habitats for the Sharp-tailed Snake are naturally fragmented, and land conversions, road
building, and other human activities continue to accentuate this fragmentation both at broad
(across the species’ Canadian range) and fine (within habitats occupied by local populations)
spatial scales. Apparently suitable, potential habitat for the Sharp-tailed Snake exists in the Gulf
Islands and southern Vancouver Island, but its extent has not been fully assessed. Very little is
known about the dispersal abilities of this species, and thus the ability of the Sharp-tailed Snake
to colonize unoccupied habitats is unknown but is suspected to be low. Habitat fragmentation
due to both human activities and natural barriers is likely to hinder dispersal movements. At a
finer scale (within a site), roads, driveways, lawns, and other developments contribute to habitat
fragmentation. In particular, known localities on the Gulf Islands are within residential areas in
highly fragmented landscapes. Increased fragmentation exposes snakes to accidental mortality,
including road kill (see below), and may constrain movements of the majority of the population
and access to essential habitat components.
3. Habitat degradation
Where the species occurs within residential areas, landscaping and gardening practices can result
in habitat degradation. The degradation of potential oviposition and hibernation habitats is of
particular concern (COSEWIC 1999). Activities that include removal of rocks and other cover
decrease habitat quality for the snakes, as well as possibly resulting in accidental crushing of
snakes. Inadvertent mortality of snakes has occurred during lawn-mowing and mechanical weedtrimming. Introduced invasive plants (such as Himalayan blackberry, Rubus discolor, and Scotch
broom, Cytisus scoparius) are prevalent at many of the localities occupied by the Sharp-tailed
Snake. Although habitat structure is likely to be more important for snakes than specific
composition of plant species, dense monocultures of invasive, introduced plants may reduce
gastropod prey, shade basking sites, and decrease habitat complexity. Encroachment of
coniferous forest on more open woodlands and Garry oak meadows is also likely to degrade
Sharp-tailed Snake habitats. In the past, periodic burning maintained these ecosystems, and fire
suppression over the past 150 years has changed the natural disturbance regimes. In addition to
wildfires, aboriginal peoples used controlled burning to maintain meadow and woodland habitats
on southern Vancouver Island for harvesting of plants and wildlife (Cook 2004).
9
Recovery Strategy for the Sharp-tailed Snake
August 2008
4. Road mortality
Snakes are vulnerable to road mortality when moving within or between their seasonal habitats
in fragmented landscapes. Reports exist of six specimens of the Sharp-tailed Snake found dead
on roads (five on North Pender and one on South Pender islands), including three specimens on
North Pender Island in the autumn of 2003 (Spalding 1995; Engelstoft and Ovaska 1999; C.
Engelstoft, pers. comm., 2008). The significance of road mortality to populations of the Sharptailed Snake is unknown but can be expected to increase concomitant with a growing human
population and vehicle traffic. One Sharp-tailed Snake site is in the immediate vicinity of a ferry
terminal on Saltspring Island, which has experienced about 45% annual increase in vehicle
traffic within the past decade (from 147,830 vehicle trips in 1992–1993 to 214,787 trips in 2001–
2002; B. Bourquin, pers. comm., 2002). Another site on Vancouver Island is bisected by a
popular recreational trail, and mortality from collisions with bicycles is a possibility although
undocumented.
5. Predation
All known Sharp-tailed Snake sites in the Gulf Islands are close to human habitation with
associated domestic and feral animals (for example, introduced pheasants). One snake was found
dead on a driveway, probably killed by a cat (Spalding 1995). Several snakes found at this site
had scarring consistent with attempted predation by birds (either native or introduced)
(Engelstoft and Ovaska 1999). The magnitude of threat posed by native and introduced predators
to this species is unknown.
6. Use of molluscides/pesticides
Pesticide use could adversely affect snakes. If molluscides, such as metaldehyde slug bait, are
used, the prey base of the Sharp-tailed Snake, including native species of slugs, might be
affected. It is also possible that feeding on animals that have consumed molluscides harms
snakes. High densities of introduced European land snails (particularly Helix aspersa) have been
recorded from one site where the Sharp-tailed Snake occurs on Saltspring Island (D. Fraser, pers.
comm., 2002). This snail is on the list of pests regulated in Canada (Canadian Food Inspection
Agency 2005), and its spread is of concern to Agriculture Canada due to the snails’ invasive
habits and threat to agricultural products. In this case, the Canadian Food Inspection Agency has
agreed to use manual control rather than chemical molluscides to control the introduced snail
Helix aspersa (D. Fraser, pers. comm., 2002). However, broadcast of pesticides to control this or
other invasive species of gastropods at other sites could adversely affect the Sharp-tailed Snake
and its natural prey base.
7. Direct persecution of snakes
Although no venomous species are present in coastal B.C., snakes often have an unfavourable
public image that may lead to persecution. The Gulf Islands and parts of Vancouver Island are
experiencing a relatively high rate of population growth and expanding tourism. Both of these
factors increase the probability of people encountering snakes.
10
Recovery Strategy for the Sharp-tailed Snake
August 2008
Actions Already Completed or Underway
Recovery work already completed or underway includes the following:
Habitat protection
•
Stewardship agreements (legally non-binding) signed by private landowners at most
Sharp-tailed Snake sites and several other sites with suitable habitat for the species on
Saltspring, North and South Pender, and Vancouver islands (by Habitat Acquisition Trust
and Salt Spring Island Conservancy; 2005–2008).
•
A conservation covenant was established in 2004 on a residential property on North
Pender Island to protect a small but important rocky knoll used by the Sharp-tailed
Snake.
•
Information on habitat protection measures for the species has been provided to Islands
Trust planners and North Pender Island Local Trust Committee Members. Development
permit areas in the revised North Pender Island Official Community Plan and include
Sharp-tailed Snake habitat (by Habitat Acquisition Trust and Salt Spring Island
Conservancy).
•
Guidelines for protecting the habitat of this species were incorporated into the document
Best Management Practices for Amphibians and Reptiles in Urban and Rural
Environments in British Columbia (Ovaska et al. 2003).
Inventories and research
•
Multi-year habitat assessment and survey project through the Government of Canada
Interdepartmental Recovery Fund (IRF) on properties of numerous federal
departments/agencies, Department of National Defence (DND), Parks Canada, and
National Research Council (NRC):
¾ Gulf Islands National Park Reserve, 2002 (Engelstoft et al. 2002), followed by
inventories in 2003–2007, ongoing (Engelstoft 2004, 2005, 2007, ongoing)
¾ DND properties on southern Vancouver Island, 2003–2007, ongoing (Engelstoft
2004, 2005, 2007, ongoing)
¾ NRC property on southern Vancouver Island (2007, ongoing)
¾ Coast Guard lands on Discovery Island (2004–2005)
¾ Transport Canada lands on Saltspring Island (2007)
•
Population monitoring and capture-recapture study at a DND property (2004–2007,
ongoing; Engelsoft 2004, 2005, 2007; Ovaska and Engelstoft 2005).
•
Habitat assessment and surveys within Capital Regional District (CRD) Parks and Trails
System:
¾ Galloping Goose Regional Trail right-of-way in Metchosin, near earlier records
(Engelstoft 2002)
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Recovery Strategy for the Sharp-tailed Snake
August 2008
¾ All major Capital Regional District parks (2006–2008, ongoing) (Engelstoft 2006 and
pers. comm., 2008)
•
Surveys of private lands on Saltspring, Pender, Mayne, Galiano, and Vancouver islands
(ongoing); Habitat Acquisition Trust and island conservation groups on Gulf Islands.
•
Thermal ecology studies, 2003 (Isaac and Gregory 2003).
•
Habitat characterization studies, 2004 (Wilkinson and Gregory 2005).
•
Research into distribution, ecology, and movements, 1996–2000 (Engelstoft and Ovaska
1997, 1998, 1999; Ovaska and Engelstoft 2000).
Habitat restoration
•
Habitat restoration at eight private properties on Saltspring Island, 2002–2008 (Meier
2001; C. Engelstoft, pers. comm., 2008).
Extension materials produced
•
Sharp-tailed Snake identification guide. 2006. B.C. Ministry of Environment.
•
Training video produced by DND.
•
Sharp-tailed Snake. 2004. Wildlife in British Columbia at Risk Series. Habitat
Conservation Trust Fund (HCTF) and B.C. Ministry of Water, Land and Air Protection
(B.C. MWLAP).
•
Attracting snakes into your backyard — tips for reptile-friendly landscaping and
gardening. 2003. Brochure funded by Habitat Stewardship Program, HCTF, and B.C.
MWLAP.
•
Sharp-tailed Snake, Contia tenuis. 2002. British Columbia’s Wildlife at Risk Series. Fact
sheet produced by B.C. MWLAP.
•
Stewardship workshop package (including PowerPoint presentation), 2002–2003; funded
by HSP.
Collaboration
The Sharp-tailed Snake Recovery Team has formed working partnerships with several groups
and agencies whose participation is crucial to successful recovery of this species.
Team participants and partners include the following:
Government agencies and organizations (federal, provincial)
• B.C. Ministry of Environment
• Canadian Forest Service
• Canadian Wildlife Service
• Department of National Defence
• Parks Canada
12
Recovery Strategy for the Sharp-tailed Snake
August 2008
Local governments
• Capital Regional District Parks
Non-government organizations
• Garry Oak Ecosystems Recovery Team
• Habitat Acquisition Trust
• Islands Trust
• Galiano Conservancy Association
• Mayne Island Conservancy Society
• Pender Islands Conservancy Association
• Salt Spring Island Conservancy
• University of Victoria
In addition, contacts with private landowners have been established as a part of research and
stewardship programs at several sites.
Knowledge Gaps
Knowledge gaps directly related to recovery planning have been identified in the following
areas: (1) habitat availability and assessment; (2) distribution and area of occupancy; (3) habitat
requirements and critical habitat description; (4) life history and movements; and (5) population
genetics. The most pressing issues that need to be addressed are habitat assessment across the
species’ range, possible existence of undocumented populations, and details of habitat
requirements.
1. Habitat availability and assessment. Potentially suitable habitat exists in many areas of the
Gulf Islands and southern and eastern Vancouver Island but, apart from small areas, its
suitability for the Sharp-tailed Snake has not been systematically assessed. Information on
habitat suitability across the species’ potential Canadian range within the Georgia Basin
Ecoprovince is needed to locate possible undocumented populations and to address habitat
protection needs and habitat connectivity issues at a broad scale. Information is also needed
on the occurrence of the species within protected areas, which could function as core areas
for recovery efforts.
2. Distribution and area of occupancy. Many potential habitats within the species’ range have
been surveyed inadequately or not at all. Increased search effort in recent years has resulted
in the documentation of several new occurrences, but additional undocumented populations
may well exist. It is important that these populations are located, so that threats to them can
be assessed and protection measures applied as needed. In addition, more accurate
information on the distribution of the species is required to better assess the status of
populations and habitat protection needs across the species’ range. At a smaller scale,
information on the area of occupancy at known sites is needed for assessing threats to local
populations, evaluating detailed habitat restoration and protection requirements, and
obtaining estimates of population size.
13
Recovery Strategy for the Sharp-tailed Snake
August 2008
3. Habitat requirements and critical habitat description. Specific features of habitats required by
the snakes for their seasonal and/or daily activities are poorly known. Information on habitats
or habitat features needed for oviposition, foraging, thermoregulation, and hibernation is
needed to accurately identify critical habitats for this species. In addition, the effectiveness of
specific habitat restoration measures is unknown, including landscaping practices
implemented as a part of stewardship programs.
4. Life history and movements. Many aspects of the life history and behaviour of the Sharp-tailed
Snake remain unknown, including patterns of survival and recruitment and reproductive
parameters such as clutch size and frequency and timing of oviposition. This information is
needed to assess population viability and reproductive potential. Information is also needed
on dispersal, seasonal, and short-term movements of individual snakes, which would
elucidate their colonizing ability, responses to habitat fragmentation, and threat from road
mortality.
5. Population genetics. Known populations of the Sharp-tailed Snake in British Columbia are
small and isolated from each other, and hence they may be subject to loss of diversity
through genetic bottlenecks and inbreeding. Genetic material from snakes from the Gulf
Islands was donated for phylogenetic studies of Contia across its range, but DNA was
obtained only from a limited number of B.C. samples (M. Blouin, pers. comm., 2001; 1
sample, from North Pender Island: C. Feldman, pers. comm., 2008). The results suggest that
snakes from B.C. are part of a widespread mtDNA lineage within Contia tenuis, similar to
samples from Washington and parts of Oregon and California (C. Feldman, pers. comm.,
2008). However, finer-scale differences such as the degree of genetic differentiation among
populations from different islands are unknown.
RECOVERY
Recovery Feasibility
Recovery of the Sharp-tailed Snake is feasible because multiple populations with reproductive
individuals exist, and the available habitat is thought be sufficient to support populations,
provided that threats are reduced (see below for analysis).
1. Are individuals capable of reproduction available to support recovery? – Yes
Several populations of the Sharp-tailed Snake are known, and additional populations may
be found with more survey effort. Populations may be larger than suggested by the
relatively few observations, as these snakes are secretive and appear to spend much of
their time underground. Individuals may live a decade or more and populations can thus
withstand several years of adverse conditions and low recruitment.
2. Is sufficient habitat currently available to support recovery? – Yes
Apparently suitable habitat for this species exists in many areas of the Gulf islands and
southern and eastern Vancouver Island. Some of these habitats are within protected areas
(regional, provincial, and national parks). Surveys of apparently suitable habitat have
14
Recovery Strategy for the Sharp-tailed Snake
August 2008
already resulted in discovery of new sites and an increase in area of occupancy at known
sites.
3.
Can significant threats to the species or its habitat be avoided or mitigated through
recovery actions? – Yes
The primary threat to this species is habitat loss. However, these snakes require relatively
little space and can coexist with humans, provided that certain precautions are taken and
key habitat features are protected. Stewardship measures already undertaken (such as
workshops in selected communities near known Sharp-tailed Snake sites and close
collaboration with landowners and land managers) have proved successful to date in
protecting and restoring habitat.
4. Do the necessary recovery techniques exist and are they known to be effective? – Yes
Standard techniques are required to recover the species, and efforts to date, such as
stewardship activities, are already successful.
Recovery Goal
The long-term goal (over the next 20 years) of this recovery strategy is to ensure the persistence
of the Sharp-tailed Snake across its natural range in Canada. The short-term goal (over the next 5
years) is to ensure the persistence of Sharp-tailed Snake populations at each known site and to
prevent the loss of habitat important to the species’ survival and recovery.
Rationale for the Recovery Goal
The Sharp-tailed Snake has a naturally small distribution in Canada, and the numbers of
populations is low and occur within fragmented habitats. Therefore, the key to recovery of this
species is removing threats to its habitat (through habitat securement) and ensuring that possible
undocumented populations are located through expanded survey efforts. Down-listing may be
possible, if threats to the habitat can be removed and/or a significant number of undocumented
populations are discovered. Additional information (to be obtained through objectives five and
six below) is required before we can define quantitative recovery targets.
Recovery Objectives
1. Protect all known Sharp-tailed Snake habitat and populations.
2. Prevent fragmentation of habitat within occupied sites.
3. Investigate the existence of additional populations throughout the species’ Canadian
range, including suitable habitats outside the known range within the Georgia
Depression Ecoprovince.
4. Protect habitats important to the species’ survival and recovery as they are identified.
5. Reduce gaps in our knowledge of the species’ habitat requirements.
6. Reduce gaps in our knowledge of the species’ population ecology.
7. Increase awareness of the Sharp-tailed Snake and its habitats.
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Recovery Strategy for the Sharp-tailed Snake
August 2008
Approaches Recommended to Meet Recovery Objectives
The approaches outlined in Table 2 have been grouped into the following broad strategies:
habitat protection, habitat stewardship, habitat inventory, population inventory, research, and
outreach. These strategies, in turn, address the objectives listed above and respond to the threats
identified for populations of the Sharp-tailed Snake in Canada. The following threats are
addressed:
1. Habitat loss. This threat is addressed through habitat protection, stewardship strategies,
and inventories. The strategy to prevent further habitat loss includes proactively
approaching land managers and planners, and encouraging the incorporation of habitat
needs of this species into management and land use plans (i.e., Official Community
Plans). Stewardship initiatives address habitat protection on private lands. Assessing
habitat throughout the species’ range, followed by surveying for snakes, is a first step
towards protecting habitats of possible undocumented populations. Surveys should focus
both on habitats that are already protected, as they may form core areas for recovery
efforts, and on areas that require additional management or protection measures.
2. Habitat fragmentation at broad and fine scales. These threats are addressed through
habitat protection, stewardship strategies, and habitat inventories. At the landscape scale,
the approach is to proactively incorporate habitat needs of the species into land use and
management plans. Habitat assessment throughout the species’ range will provide
information on fragmentation and isolation of suitable habitats and on opportunities to
maintain connectivity, for example, through strategic land use planning or acquisition. At
finer scales, at known Sharp-tailed Snake sites, stewardship initiatives are to focus on
landowners and managers to maintain habitat connectivity.
3. Habitat degradation. This threat is addressed through habitat protection and stewardship
activities. Habitat protection measures are aimed at protecting important habitat
components, such as presumed egg-laying habitats, from disturbance. Stewardship
activities focus on collaboration with land managers and owners to encourage practices
that maintain habitat features required by the snakes and to curtail harmful activities, such
as intensive landscaping.
4. Road mortality. This threat is addressed through stewardship, threat clarification, and
research strategies. As a proactive measure, close contact with landowners and managers
is encouraged through stewardship initiatives to ensure that no new roads are built near
known Sharp-tailed Snake habitats. At present, the significance of road mortality to
Sharp-tailed Snake populations is unknown, and monitoring mortality on public roads
near known sites with a potential problem is a first step to address this issue.
Other threats. Other threats dealing with habitat degradation and inadvertent mortality of snakes
are addressed through outreach. Outreach activities include strategic distribution and display of
stewardship and interpretive materials; delivery of workshops; and other initiatives that increase
public awareness, appreciation, and understanding of the snakes and their habitats.
16
Recovery Strategy for the Sharp-tailed Snake
August 2008
Recovery planning table
Table 2. Recovery planning table for the Sharp-tailed Snake.
Priority Obj. Threat or
Broad strategy to Recommended approaches to meet recovery
no.
limiting
address threats
objectives
factor
addressed
1
1, 2,
4
Habitat loss &
fragmentation
Habitat protection
1
1, 2,
7
Habitat loss &
fragmentation;
habitat
degradation
Habitat stewardship
2
5, 7
Habitat stewardship
1
3, 4
1
3, 4
Habitat loss;
habitat
degradation
Habitat loss &
fragmentation
NA
2
5, 6
NA
2
1, 2
NA
2
1, 2
Road mortality
3
7, 3
Habitat loss/
fragmentation;
habitat
degradation;
inadvertent
mortality or
persecution
Habitat inventory
Population
inventory and
monitoring
Population
inventory and
monitoring;
research
Population
inventory and
monitoring
Threat clarification/
research
Outreach
- Collaborate with regulators to include habitat
protection measures into land use plans (e.g.,
development permit areas in Official Community
Plans)
- Encourage parks planners and managers with
municipal, regional, provincial, and federal
governments to survey for and manage this species on
their lands
- Encourage First Nations groups to survey for and
manage this species on their lands
- Encourage private landowners (including developers)
to formally protect key habitats (e.g., through
covenants)
- Collaborate with developers near known sites to
ensure protection of important habitats and
maintenance of habitat connectivity
- Establish or continue contacts with land managers and
landowners at all known sites
- Engage in habitat restoration/ enhancement projects
with landowners and volunteers to promote active
involvement and habitat stewardship
- Assess effectiveness of restoration projects through
monitoring and research, involving landowners and
volunteers
- Assess habitat suitability throughout the species’
Canadian range
- Conduct surveys of high-suitability habitats, as
identified through habitat assessment
- Conduct surveys at historical sites to determine
occupancy
- Monitor population trends at selected sites
- Obtain information on seasonal habitat use and
movements
- Obtain information on life history
- Determine the extent of the distribution at known sites
- Assess threats from habitat fragmentation and road
mortality at each known site
- Collect information on road mortalities through
surveys and community outreach
- Make stewardship and interpretive materials available
to targeted audiences at strategic locations
- Prepare new materials as needed (e.g., an
identification brochure)
- Conduct workshops at selected locations
17
Recovery Strategy for the Sharp-tailed Snake
Priority
Obj.
no.
1
3
August 2008
Threat or
limiting
factor
addressed
Broad strategy to
address threats
Recommended approaches to meet recovery
objectives
5
NA
Research
6
NA
Research
- Conduct research on habitat use, including daily and
seasonal pattern of movements
- Identify important habitat features and components for
oviposition, hibernation, and foraging
- Conduct research into the species’ life history,
demography, and ecology
- Conduct research into the population genetics to
elucidate the degree of isolation and uniqueness of
different B.C. populations
- Develop partnerships with universities & other
agencies to promote research on all aspects of the
species’ biology throughout its range
Description of the recovery planning table
A. Habitat protection. The primary focus of this recovery strategy is to ensure that further loss
and fragmentation of habitats of the Sharp-tailed Snake are prevented. Protection measures
are to focus on habitats at known sites and surrounding areas. Possible new localities are to
be incorporated into the process as they are discovered. This approach to habitat protection
involves collaboration with managers and planners to incorporate habitat protection needs of
this species into the planning process at different levels. The feasibility of land acquisitions
and the establishment of covenants are to be investigated.
B. Habitat stewardship. Because several known sites are on private lands, working closely with
landowners is a priority. Initiating and maintaining personal contacts with landowners of all
properties where the Sharp-tailed Snake occurs will provide a proactive approach to protect
key habitat features and to anticipate changes in either ownership or land use. Landowners
are to be encouraged to protect Sharp-tailed Snake habitat and collaborate with researchers in
monitoring populations. Habitat restoration/enhancement projects are to be conducted as
needs for these activities are identified and as opportunities arise. Restoration projects on
private lands foster stewardship by bringing together volunteers, landowners, and researchers.
Monitoring the use of the restored habitat by snakes is essential to assess the effectiveness of
the measures and whether similar measures are expected to be useful at other sites.
C. Habitat inventory. A first step towards locating possible undocumented populations is to
assess habitat suitability across the species’ Canadian range. Such an assessment has already
been prepared for portions of the species’ range; habitats within remaining areas with suitable
habitat on Vancouver Island and Gulf Islands are to be similarly assessed. Whether suitable
habitat exists on the mainland B.C. within the Georgia Depression Ecoprovince also needs to
be examined. A broad-scale assessment is to be followed by detailed, finer-scale assessments
of selected priority areas. Habitat features to be incorporated in the assessment include forest
and vegetation cover, rocks and coarse woody debris, aspect, slope, and other terrain features.
D. Population inventory. Inventory efforts are to target three types of areas: (1) high-quality
habitats identified through habitat assessment to locate possible new populations; (2) known
18
Recovery Strategy for the Sharp-tailed Snake
August 2008
sites to provide information on the extent of local distribution; and (3) areas with historical
records of the species that either have not been surveyed or have received little survey effort
in recent years. High-quality habitats both in protected areas and outside these areas are to be
surveyed.
E. Threat clarification. Road mortality poses a potential but unknown threat to Sharp-tailed
Snake populations. The strategy consists of examining the degree of habitat fragmentation by
roads at all known sites and assessing potential threats. Where needed, field surveys are to be
conducted to examine movements of snakes across roads and/or incidence of road-kill.
Landowners and residents near known Sharp-tailed Snake sites are to be encouraged to
collect and report road-killed snakes.
F. Outreach. This strategy consists of (1) distribution of information and interpretive materials to
targeted audiences at strategic locations, such as near known distribution records; (2)
preparation of new interpretive materials, such as an identification brochure; and (3) delivery
of workshops in communities near known or potential Sharp-tailed Snake habitat. In addition
to raising awareness of the species and its habitats, workshops help to establish contacts with
landowners and locate new sites from reports by the public.
G. Research. Research is needed into several aspects of the species’ biology. The most urgent
need is to collect information on habitat use patterns, including seasonal pattern of habitat
use, movements, thermal ecology, and important micro- and macro-habitat features. This
information is needed to identify critical habitats. Other data gaps exist with respect to
isolation and genetic structure of different populations in B.C., demographic patterns, and life
history parameters; research into all these aspects is to be encouraged. Information on the
genetic structure of populations will help direct recovery efforts and to assess significance of
habitat fragmentation; information on demographic and life history parameters provide
information on recovery potential and are essential for assessing and monitoring population
viability.
Performance Measures
Objective 1: Protect all known Sharp-tailed Snake habitat and populations
• On private lands, percentage of known sites where landowners or residents are
actively involved in stewardship through restoration, population monitoring, habitat
protection, or other activities
• On private lands, percentage of sites where landowners have signed stewardship
agreements or established conservation covenants
• On public lands (federal lands, provincial, municipal), percentage of sites where
management measures for the species have been implemented
• Percentage of sites considered secure on private and public lands
• Evidence of long-term persistence of snake populations at sites where management
actions (stewardship and protection) have been implemented
Objective 2: Prevent fragmentation of habitat within occupied sites
19
Recovery Strategy for the Sharp-tailed Snake
•
•
•
August 2008
Number of land use or development plans with provisions for habitat of the Sharptailed Snake and the percentage of suitable habitat that they cover
Number of sites where habitat fragmentation is reduced or prevented through
management actions
Evidence of long-term persistence of snake populations at landscape level in areas
where management actions (stewardship and protection) have been implemented
Objective 3: Investigate the existence of additional populations throughout the species’
Canadian range, including suitable habitats outside the known range within the
Georgia Depression Ecoprovince
• Percentage of the Georgia Basin Ecoprovince and subzones assessed for habitat
suitability at broad and fine scales
• Percentage of high-suitability habitats surveyed for the species
• Number of new localities found for the species (through survey efforts or reports
from the public)
Objective 4: Protect habitats important to the species’ survival and recovery as they are
identified
• Percentage of newly identified habitats where management, stewardship, or other
protection measures are applied
Objective 5: Continue to reduce gaps in our knowledge of the species’ habitat requirements
• Movement patterns and seasonal habitat use clarified
• Important habitat components, such as oviposition, hibernation, and foraging sites,
described
• More accurate description of critical habitat produced, as a result of addressing
knowledge gaps
Objective 6: Continue to reduce gaps in our knowledge of the species’ population ecology
• Information obtained on population trends and demography
• Life history features and requirements clarified
• More accurate information produced on management requirements, as a result of
addressing knowledge gaps
Objective 7: Increase awareness of the Sharp-tailed Snake and its habitats
• Number of landowners or community members involved in various stewardship
activities
• Number of new sites discovered as a result of public input
Critical Habitat
Identification of the species’ critical habitat
Critical habitat for the Sharp-tailed Snake in B.C. cannot be identified at this time, but it may be
identified at a later date, in an addition to the recovery strategy posted by Environment Canada
20
Recovery Strategy for the Sharp-tailed Snake
August 2008
or in a future action plan. Habitat needs of the Sharp-tailed Snake are poorly known, and more
definitive information on the species’ distribution must be obtained before any specific sites can
be formally proposed as critical habitat. It is expected that critical habitat for the Sharp-tailed
Snake will be identified following: (1) completion of outstanding work required to quantify
specific habitat and area requirements for these species, as described in Table 3, and (2)
consultation and development of stewardship options with affected landowners and managers.
In B.C., areas where the Sharp-tailed Snake has been found consist of small forest openings with
abundant cover, such as talus, coarse woody debris, and/or fissures in rock (COSEWIC 1999;
Engelstoft 2004, 2005, 2006, 2007). Known sites have either a southern or western aspect,
shallow soil and litter cover, and relatively high rock cover (Wilkinson and Gregory 2005).
Proximity to the forest and moist foraging areas is also thought to be important, but this aspect of
the species’ habitat requirements is poorly understood. Seasonal habitat use, including locations
of hibernation and oviposition sites in relation to summer foraging areas, is poorly known. This
information is logistically difficult to obtain for this rare and secretive species.
At all known sites, the area occupied by the species appears to be relatively small. However, the
area of occupancy is difficult to estimate accurately because of the species’ secretive habits,
apparent low densities, and paucity of information on movement patterns. These characteristics
also make it problematic to confirm the extent of distribution of Sharp-tailed Snakes at known
sites.
A schedule of studies outlining the work necessary to identify critical habitat is shown below.
Recommended schedule of studies to identify critical habitat
Table 3. Schedule of studies required for the identification of critical habitat.
Description of activity
Outcome/rationale
Complete broad-scale habitat suitability assessment
throughout the species’ Canadian range
Survey all broad areas that have not been previously
covered
Collect detailed information on seasonal habitat use
and movements in disturbed and more natural
habitats
Identify characteristics of important habitat features
and components, such as oviposition and hibernation
sites, and foraging areas
Prepare a habitat model based on survey results and
research
- Produces habitat suitability maps to
direct inventory effort
- Fills in knowledge gaps of the species
distribution
- Identifies opportunities for enhancing
habitat connectivity
- Fills in knowledge gaps of the species’
distribution
- Clarifies spatial requirements
Timeline
2008–2010
2008–2012
2008–2012
- Identifies key components of critical
habitat
2008–2012
- Allows delineation of remainder of
critical habitat in unsurveyed areas
2010–2011
Existing and Recommended Approaches to Habitat Protection
Most of the land base within the range of the Sharp-tailed Snake is privately owned. In total,
only about 5% of forested areas within the Coastal Douglas-fir biogeoclimatic zone are within
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Recovery Strategy for the Sharp-tailed Snake
August 2008
protected areas (B.C. MOE 2002). Within the Capital Regional District, about 34% of remaining
older forest occurs within parks (CRD 2003). In the Gulf Islands, sensitive ecosystems occur in
fragmented patches, which are largely outside of protected areas (CRD 2003). These areas
include older forests, coastal bluffs, and woodlands, some of which provide potential habitat for
the Sharp-tailed Snake.
The Gulf Islands National Park Reserve protects about 33 km2 (including a 25-m intertidal zone)
in the southern Gulf Islands (Parks Canada 2007). The park includes land on North and South
Pender, Saturna, and Mayne islands, as well as on a number of smaller islands. Several of the
park properties contain potential habitat for the Sharp-tailed Snake (Engelstoft et al. 2002), but
as of March 2008, the species has only been located at one site within the park — Greenburne
Lake on South Pender (Engelstoft 2007). The CRD Parks and Trails system includes 28 parks
and 2 trails that protect 11,500 ha of land (CRD 2008b). The parks range from under 2 to
4100 ha, and most of them are small. Several B.C. provincial parks with suitable habitat for the
species are on southern Vancouver Island (e.g., Sooke Potholes, Gowlland Tod, John Dean, and
McDonald provincial parks) and adjacent small islands.
The ownership of the five occurrences of the Sharp-tailed Snake on Vancouver Island is as
follows:
• Site 1 (Metchosin): federal land (DND), right-of-way regional trail (Galloping Goose
Regional Trail, CRD Parks), and adjacent private, rural residential land;
• Site 2 (Sooke Hills): private, rural residential land;
• Site 3 (Langford): regional park (Mill Hill, CRD Parks);
• Site 4 (Saanich): federal land (DND), regional park (Mount Work, CRD Park), municipal
park (Highlands District), and private, rural residential land; immediately adjacent to
Gowlland Tod Provincial Park; and
• Site 5 (Saanich): federal (National Research Council property), surrounded by private,
rural residential lands.
On the Gulf Islands, all occurrences are mostly from private, urban, or rural residential lands.
The exceptions are portions of two sites: (1) Greenburne Lake within the Gulf Islands National
Park Reserve on South Pender Island, and (2) B.C. provincial land at the Vesuvius ferry terminal
on Saltspring Island.
The public lands where the species have been found are used for multiple purposes, including
military training (DND lands) and recreational activities (CRD parks and trails; Gulf Islands
National Park Reserve). DND and Parks Canada are actively surveying and managing habitat for
this species through collaboration with researchers. CRD Parks have similarly taken an active
role on their lands. It is important to continue surveys on these lands and to initiate surveys on
other public lands, such as B.C. provincial parks, several of which contain suitable habitat and
are in areas adjacent to known occurrences. Many provincial, regional, and local parks within the
Capital Regional District are small and receive intense recreational use, which may threaten the
species if not managed. Information on distribution of the species within both protected and
unprotected areas is essential to effectively manage and mitigate threats from human uses. On
private lands, the recommended approach to conservation is by promoting stewardship activities
and involving landowners and community members in habitat protection and restoration. Such
22
Recovery Strategy for the Sharp-tailed Snake
August 2008
efforts are underway in some communities on the Gulf Islands and have already proven
successful.
Effects on Other Species
In addition to the Sharp-tailed Snake, the habitat protection, stewardship, and outreach strategies
outlined in Table 2 are expected to benefit other components of the ecosystem. The benefits will
extend to Garry oak–arbutus ecosystems, which are at risk in B.C.
Surveys for the snakes could disturb the habitat if carried out carelessly. However, adverse
effects can be eliminated or minimized by taking proper precautions, which include replacing all
natural cover searched, avoiding disturbance to unstable talus slopes, and consulting a botanist
before placing artificial cover-objects in sensitive habitats, such as within Garry oak ecosystems.
Socioeconomic Considerations
Socioeconomic impacts of the recovery strategies described in this document could affect new
residential developments and associated infrastructure, including road building. Possible effects
include changes to location or configuration of new developments or roads, and changes to
management practices. These impacts are expected to be minor. On private lands, the focus is on
voluntary stewardship activities, most of which can be implemented with little or no monetary
cost. Rather than burdening developers or residents, these actions may actually enhance the value
of the properties by creating an environmentally friendly image. The geographic scale of the
impacts is restricted to known sites and their immediate vicinity and to new sites that are
potentially found through increased survey efforts.
The Sharp-tailed Snake has high potential as a subject for environmental awareness and
educational programs. These snakes are harmless and are considered beneficial as their diet
consists largely of slugs, including introduced garden pests. The Sharp-tailed Snake could serve
as a focal species for conservation of natural areas within the Coastal Douglas-fir biogeoclimatic
zone, including rare Douglas-fir–arbutus and Garry oak plant communities.
Statement on Action Plans
An action plan is in preparation and is to be completed before or by 2015.
23
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August 2008
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PERSONAL COMMUNICATIONS
Blouin, M. Department of Zoology, 3029 Cordley Hall, Oregon State University, Corvallis, OR
97331-2914. Tel: (541) 737-2362; Fax: (541) 737-0501; e-mail: [email protected]
(contacted by K. Ovaska in May 2001).
Bourquin, B. BC Ferries statistics division (contacted by L. Blight in September 2002).
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Recovery Strategy for the Sharp-tailed Snake
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Engelstoft, C. Alula Biological Consulting (contacted by K. Ovaska in March 2008).
Feldman, C. Department of Biology, Utah State University, Logan, UT 84322-5305; Tel: (435)
797-7625; Fax: (435) 797-1575; e-mail: [email protected] (contacted by C. Engelstoft
in March 2008).
Fraser, D. Species At Risk Specialist, B.C. Ministry of Environment (Conservation Planning
Section), PO Box 9374 Stn Prov. Gov., Victoria, BC V8W 9M4; Tel: (250) 387-9756; email: [email protected] (contacted by L. Blight in September 2002).
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